The LCD device has been widely used in various electric devices such as TV, personal computer, tablet personal computer, PDA, phone, digital camera, and so on, due to characteristics of thin thickness, low power consumption and low radiation etc. The LCD device usually includes a gate driving circuit, a source driving circuit, a plurality of scanning lines, a plurality of data lines, and a plurality of pixels formed by intersection of the plurality of scanning lines and the plurality of data lines. The plurality of scanning lines is connected to the gate driving circuit. The gate driving circuit is used to provide gate driving signals to the plurality of pixels through the plurality of scanning lines. The plurality of data lines is connected to the source driving circuit. The source driving circuit is used to provide display signals to the plurality of the pixels through the plurality of the data lines.
At present, the LCD device usually use the polarity inversion driving manner which means that a positive polarity and a negative polarity of voltages of the display signals provided to every pixel by the source driving circuit alternately change. For example, in a frame time, the polarity of the voltage of the display signal provided to a pixel by the source driving circuit is positive, and in next frame time, the polarity of the voltage of the display signal provided to the pixel by the source driving circuit is negative. The polarity inversion driving manner includes frame inversion, row inversion, column inversion and dot inversion. Please referring to FIG. 1, FIG. 1 is a schematic view of voltage polarity of the dot inversion. FIG. 1 shows 4 row*4 column pixels, as shown in FIG. 1, the dot inversion means that the polarities of the voltages of the display signals provided to every two adjacent pixels are different in every frame time, and in a next frame time, the polarity of the voltage of the display signal provided to each pixel is different from that in a former frame time.
It needs power consumption that the polarity of the voltage is changed from negative to positive. In the LCD device using the polarity inversion driving manner, the source driving circuit needs to change the polarities of display voltages once when every frame is refreshed, so it needs large power consumption. Especially in the LCD device using the dot inversion driving manner, the source driving circuit changes voltage polarities of the display signals provided by output channels corresponding to every data line once when every scanning line is scanned by the gate driving signal in every frame time, besides changing the polarities of the display voltages once when every frame is refreshed, so larger power consumption is needed. In order to reduce the power consumption, charge sharing technology is developed.
Please referring to FIG. 2, FIG. 2 is a schematic circuit diagram of a conventional source driving circuit. As shown in FIG. 2, the source driving circuit 10 includes a first output channel 11 and a second output channel 12. The first output channel 11 includes a first digital-to-analog converter 110, a first amplifier 112, and a first output 114. The second output channel 12 includes a second digital-to-analog converter 120, a second amplifier 122, and a second output 124. The first output channel 11 is used to provide a first output signal Output1, and the second output channel 12 is used to provide a second output signal Output2. The first output signal Output1 and the second output signal Output2 are respectively provided to adjacent two data lines of the LCD device (not shown) as display signals.
Please referring to FIG. 3, FIG. 3 is a schematic waveform diagram of the first output signal Output1 and the second output signal Output2 when the source driving circuit 10 is not using the charge sharing technology. Taking using the dot invention driving manner, a reference voltage being 4.7V, and a maximum display power consumption (such as a maximum negative voltage is 0.2V, a maximum positive voltage is 9.2V) for example, as shown in FIG. 3, voltage of the first output signal Output1 which is outputted by the first output 114 and voltage of the second output signal Output2 which is outputted by the second output 124 change between 0.2V and 9.2V at a row scanning frequency, that is, polarities of the voltages of the first output signal Output1 and the second output signal Output2 change once when a scanning line is scanned. As indicated by solid arrows, it needs power consumption that the first output signal Output1 and the second output signal Output2 change from 0.2V to 9.2V.
Please referring to FIG. 2 and FIG. 4, FIG. 4 is a schematic waveform diagram of the first output signal Output1 and the second output signal Output2 when the source driving circuit 10 uses the charge sharing technology. A switch 13 is added between the first output 114 of the first output channel 11 and the second output 124 of the second output channel 12. The switch 13 is controlled by a charge sharing control signal CSC. As shown in FIG. 4, after the source driving circuit 10 drives a load, that is, when every scanning line is scanned, after the source driving circuit 10 provides the display signals to corresponding pixels, the charge sharing control signal CSC controls the switch 13 turn on to make the first output 114 and the second output 124 share charges (as indicated by hollow arrows), for example, when the first output 114 provides the first output signal Output1 of 9.2V, and the second output 124 provides the second output signal Output2 of 0.2V, the voltages of the first output 114 and the second output 124 are changed to 4.7V after the first output 114 and second output 124 share charges. On this basis, when polarities of the voltages of the first output signal Output1 and the second output signal Output2 change in next time, for example, when the voltage of the first output signal Output1 needs to change to 0.2V and the voltage of the second output signal Output2 needs to change to 9.2V, because that the voltages of the first output 114 and the second output 124 are 4.7V owing to sharing the charges, the voltage of the first output 114 needs to continue to reduce from 4.7V to 0.2V, and the voltage of the second output 124 just need to increase from 4.7V to 9.2V, then the first output signal Output1 having the voltage of 0.2V and the second output signal Output2 having the voltage of 9.2V are provided. Therefore, when the polarity of voltage change, only increasing voltage from 4.7V to 9.2V consumes current.
It follows that, the power consumption of the source driving circuit 10 using the charge sharing technology is lower than that of the source driving circuit 10 not using the charge sharing technology. However, as shown in FIG. 4, even the charge sharing technology is used, charges generated when the voltage changes from 4.7V to 0.2V are underused when the first output signal Output1 and the second output signal Output2 changes from positive voltage to negative voltage, such as from the maximum positive voltage of 9.2V to the maximum negative voltage of 0.2V.